Electric printing system



July 3, 1951 w. J. HooPER 2,558,901

ELECTRIC PRINTING SYSTEM Filed April 27, 1945 Patented July 3, 1951 s PATENT OFFICE ELECTRIC PRINTING SYSTEM William J. Hooper, Elsah, Ill., assignor, by mesne assignments, to William C. Huebner, New York,

Application April 27, 1945, Serial No. 590,704

Claims. (Cl. 101-426) This invention relates to an electric printing system, and more particularly to printing methods and apparatus wherein there is insufficient contact pressure between the printing means and the sheet being printed to effect proper transfer of the ink by conventional impression, and wherein good transfer is achieved by use of an electric current at the printing point. One feature of this invention is that it achieves all of the advantages of electric printing of kinds heretofore contemplated (such as light-weight parts, high speed of operation, etc), while at the same time achieving very good definition and printing with the use of relatively low electric voltages at the printing point. This, vis accomplished by bringing the sheet into light contact with the ink on the design bearing surface of the printing means, this contact being so light as to be insufficient alone for proper printing, and by passing a relatively high amperage, low voltage currentvthrough the ink and sheet at the printing point.

Another feature of this invention is that it provides improved means for transferring a liquid. as ink, to a sheet. as a moving web of paper; still another feature of this invention is that conditions are created such that a high degrec of efficiency of transfer is obtained without the use of high voltage; and a further feature of this invention is that it makes use of a very resilient or soft pressure means behind the web to ensure contact thereof with all portions o f the design bearing surface, while at the same time preventing any portion from having undesirably high pressure relationships with the paper and `backing cylinder. Other features and advantages of this invention will be apparent from the following specication and the drawings, in which:

Figure 'l is an elevational view, partly schematic, of one specific embodiment of my invention, an electric printing press wherein the web being printed is passed in light contact with a rotating inked type cylinder and transfer is effected partly by this light' contact and partly by a current passed through the ink and web at the printing point; and Figure 2 is an enlarged fragmentary detail view of the printing zone of the apparatus shown in Figure l.

Printing has for centuries been conventionally effected by mechanical pressure between an inked member having a design thereon and the sheet to beprinted, this being generally termed impression printing. In the last decade or so it has been found that ink can be transferred from the inked member to the sheet being printed by out contact between the inked member and the sheet. Certain arrangements of this type for electric printing are shown in such patents. as Huebner Patent 1,820,194 of August 25, 1931. and Huebner Patent 2,224,391l of December ll0, 1940,

although these arrangements have never gonev into commercial use.. AA full vdiscussion of this type of electric printing will not befurther set forth here as referenceA may be lmade to the above-mentioned patents tov supplement the present disclosure in regard to the advantages being sought. It is believed suicientto say, that elimination of need for high'mechanicalpressures enables very great reductions in the weight and power requirements of a largel press, a goal toward which the printing industry has been working for decades.

Prior to certain very recent work, all'velectrlc printing heretofore done has involved, the transfer of the ink across a definite and appreciable space; i. e., the lm of ink on the raised portions of a type cylinder, for example, had to be physically separated from such cylinder and caused to move across a space of several hundredths Aof an inch to the surface of the web being printed. Surface tension, adherence of the ink to 4,the

' metal of the type cylinder, and the like, are strong Afactors resisting the movement of small droplets ing the moving web'into very light contact with the ink von the design bearing cylinder, andby supplementing the light and insufficient pressure with electric transfer means. 'Ihe mechanical contact is not sufficiently heavy to effect satisfactory printing in the conventional manner, as this would require the high pressures and strengths which it is desired to avoid; but, by having all portions of the ink to be transferred come into actual contact with the web at the printing point, factors such as adherence to and adsorption in the web tend to assist the electrical means in separating the ink from' the design bearing cylinder and disposing it upon the web.

By this arrangement I find that Ican employ relatively low voltage differentials at the printing point, as a voltage differential in the neighborhood of 50 volts, and achieve the desired transfer or printing by the use of appreciable currents 3 at the instant of printing through a complete series circuit including the ink and web, as for example currents in the neighborhood of onetenth ampere per square inch of area at the this desired result by use of a very resilient or a very soft backing pad on the backing cylinder at the printing point, as very soft rubber providing yields of four to twelve thousandths of an inch at the printing point with pressures amounting to a matter of ounces per square inch rather than many pounds per square inch as is the case with impression printing using conventional packing. Even though the type of packing or blankets used on the pressure cylinders of news- Apaper work are termed soft, they comprise a relatively thin layer (generally in the neighborhood of one-tenth inch) of blotting paper consistency, requiring pressures amounting to several pounds or more per square inch when the type digs into the web and packing to the extent of as much as .012 inch, as frequently occurs in conventional impression printing. I also make this pad or backing means conducting, and preferably render the paper web more conducting than normal, in order to effect the desired transfers of current through the ink and web at the instant of printing with relatively low voltages across the printing gap.

In view of the newness of electric printing, `terminology peculiar to this art has not as yet come into common use, and the words used throughout this specification and claims will be those employed in the conventional printing art wherein ink transfer is effected entirely by impressions involving substantial mechanical pressures. That is, for example, the term printing is used to describe the operation of delivering ink from the inked member to the sheet being printed, although it will be understood that the word printing as used herein does not connote substantial mechanical pressure, but is used in the much broader sense of the word merely to mean transfer of a certain design from one element to another. This is analogous to the use of the term printing" in photography. where mechanical pressure is not the cause of transference of a. design from the negative to the sensitized paper. It will also be understood that when one of the rolls or printing members is spoken of as having designs formed on the surface thereof, such designs may comprise text, pictures, or anything else desired to be printed. Moreover, the designs may be formed on the surface of the printing member in relief, by intaglio or gravure. or by planographic or litho- -graphic methods. All such methods of forming or preparing a printing surface are well known in the conventional printing art and need not be described here, as is also the case in connection with methods and apparatus for delivering ink to the inked surface in desired quantities. In reading and interpreting this specification and the claims accompanying it, all terminology borrowed from the conventional printing art 4 must be given broad meaning appropriate to this rather special field.

I have made other inventions in the field of electric printing than those specifically claimed here and reference may be had in such regard to my copending applications Serial No. 564,574, filed November 22, 1944 and issued August 29. 1950, as Patent 2,520,504, and Serial No. 584,835, filed March 26, 1945.

The last-mentioned of the above applications also involves the use of light contact between the sheet and ink at the instant of printing, but employs high potential electrostatic fields to secure proper printing, as contrasted with providing a series circuit of the kind disclosed and claimed here. adapted to pass substantial currents across the printing gap at relatively low voltages.

Referring now more particularly to the specific printing apparatus shown in the accompanying drawing, a rotating type cylinder l0 acts as an ink source and has one of the circuit members of the electric printing circuit. This cylinder is mounted in conventional manner, not illustrated, to be rotated about its' axis Il and it is electrically grounded throughout. The designs, which are here illustrated as relief type of conventional cast form on the surface of a metal cylinder, are inked by means here illustrated schematically as conventional inking means comprising the ink trough I2 and the rolls i3d-d. Rotation of the cylinder I0 results in continually presenting to the printing point (the point where the cylinder comes into contact with the moving web of paper) a surface area which is at least partly coated by ink in the desired design to be transferred, the raised portions of' the type here illustrated carrying ink and the other portions of the surface being devoid of ink. v

. 'I'he sheet to be printed is here illustrated as a web of paper identified as Il, as a web of the kind commonly used in newspaper printing. This web moves over a guide roll i5, between preconditioning rolls |6a and ISb, in contact with a portion oi' the periphery of the type cylinder I0, and then over another guide roller Il. The web I4 is, of course, driven by conventional web drive means so as to have a lineal speed synchronized with the surface speed of the type cylinder I0.

The electric circuit at the printing point is developed between the cylindrical member I0, across the ink film on the surface thereof and the web I4 in contact therewith, and through a second cylindrical memberl I8. The cylindrical member I8 comprises an inner portion Isa of metal and an outer portion I8b of very resilient or yielding material having fairly good conductivity, as for example a layer of soft conducting" rubber at least V3 to A inch thick and preferably in the neighborhood of 1/2 inch thick.A

Rubber so'impregnated as to let appreciable current flow therethrough is commercially availablel under the designation of conducting rubber, in a number of grades of conductivity and yieldability, and I prefer to use a grade of relatively good conductivity but high yieldability.

The potential dlierential between the cylindrical members I0 and I8 is developed by a rela` tively low voltage power source here indicated" schematically as a battery i9, although it will' be understood that in practice motor generators or other similar conventional sources of current would be used. This source is adapted to deborhood of 100 volts or less.

/elop a potential between ground and the cylinirical member I8, this member being connected zo one terminal of the current source I9 through a variable current controlling resistance here identified as 20. I prefer to have the circuit element behind the ink, the member away from which the ink travels during printing or transfer, negative with respect to the web; and in the press here illustrated I effect this by grounding the negative side of th'e battery I9 and connecting the positive terminal thereof to the circuit element I8.

It may be that the minute ink droplets (conventional ink having graphite pigment particles suspended -in an oil base has negatively charged particles) have their movement away from the ink surface assisted by having electrons leave such surface from behind the ink in the direction in which it is desired to move the ink. Whatever the reason, however, the ink does seem to move more readily from the ink surface to the web when such surface is negative with respect to the web.

Referring now more particularly to Figure 2, it will be seen that the web I4 is in actual contact, at the printing point, with the ink film on the type faces of the cylinder I0, and with the readily resilient layer I8b of soft conducting rubber on the backing cylinder I8. In newspaper printing, for example, the web 0f paper commonly used has a thickness of about .O0-3 inch; and the relationship between the cylinders III and I8 should be such that the highest type faces depress the readily resilient layer I8b in the neighborhood of .006 inch, or at any rate suflicient to exceed any variation in type face height. When this is done, light but positive engagement of the web with all of the inked type faces, despite some slight variation in the height thereof, is ensured'. This contact, .because of the softness of the rubber layer Ib, is so light as to provide insufficient mechanical pressure to effect good impression printing in conventional manner, preferably comprising a Kpressure not exceeding one pound per square inch of area engaged at the printing point. Proper printing is then effected by supplementing this light contact with electric transfer by virtue of flowing an appreciable current through a circuit including the cylinder II, the film of ink thereon, the web I4 f and the cylinder I8, the circuit from this latter cylinder being completed through the variable resistance and the currentv supply source I9 back to ground. Heavy pressure of the kind found in conventional printing must be avoided if the advantages of light cylinders and high Speed of operation are to be retained, with a major portion of the transfer being effected electrically rather than mechanically.

Inasmuch as the conventional newspaper web comprises a relatively good insulator, particularly when dry, I contemplate preconditioning the web to increase its conductivity and permit currents of the kind I desire at the instant of printing with the use of relatively low printing gap voltage differentials, preferably in the neigh- If the specific resistivity of the rubber conducting layer Ib is moderately high, as 25,000 ohms per cubic centimeter, it may require an operating voltage of several hundred volts between the cylinder I8 and ground; but I prefer to keep the voltage differential across the printing gap (i. e.- from the outer surface of the layer Ib to the metal type faces of the cylinder I0) in the neighborhood of 500 6 volts or less. While the conductivity of the web may be affected by vapor treatment in a preconditioning chamber or the like, I am here illustrating preconditioning means for increasing its conductivity just in advance of the printing point. This preconditioning means comprises the cylindrical members or rolls I6a and I6b heretofore mentioned, another roll IGC, and a trough I6d. In order to make the paper more conductive without leaving a stain or injury of any kind on the finished work, I have used a solution of ammonium chloride (sal ammoniac) as a preconditioning agent, moistening the paper sufficiently to greatly increase its conductivity, but not wetting it or soaking it to an extent which would appreciably weaken the mechanical strength of the web. This can be effected by having the solution in the trough I6d fed by the roll I6c to the roll I6b, and from this roll to the under-surface of the web, the slight time interval between the moistening and the printing enabling sufficient pentration of the ammonium chloride solution into the web to provide good transmission of current therethrough at the printing point. As has been mentioned heretofore, this current may be of the order of one-tenth ampere per square inch of contact area with a voltage drop across the printing gap (i. e., across the web and ink film) in the neighborhood of volts. This current is high enough to cause arcing or scorching of the paper under static conditions; but at high speeds of operation such undesired effects do not occur. The heating effect of the current traveling across the printing gap (the 12R effect) helps dry the ink and enables the web coming off the cylinders to be passed to a second press over a folding bar or the like quicker than would otherwise be possible.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. Printing apparatus of the character described, including: a first rotating cylindrical member having at least .a portion of the surface thereof coated with ink to be transferred; a web of sheet'material; means for moving said web and causing it to pass closely adjacent said coated surface and with at least a portion of one surface of said web in light'contact with a portion of the ink on said coated surface, said contact being insufficient to alone effectthe desired transfer; a second rotating cylindrical member, this member having conducting means in engagement with the other surface of said sheet, this means comprising a surface layer of conducting readily resilient material; and means for passing a current through said sheet and the ink in contact therewith.

2. Printing apparatus of the character described, including: a rst rotating cylindrical member having at least a portion of the surface thereof coated with ink to be transferred; a web of sheet material; means for moving said web and causing it to pass closely adjacent said coated surface and with at least a portion of one surface of said web in light contact with a portion of the ink on said coated surface, said contact being insufficient to alone effect the desired transfer; a second rotating cylindrical member, this member having conducting means in engagement with the other surface of saidl sheet, this means comprising a surface layer of conducting readily resilient material; meansroperative on said web prior to the printing point for increasing the conductivity thereof; and means for passing a current through said sheet and the ink in contact therewith.

3. Printing apparatus of the character described, including: a first rotating cylindrical member having at least a portion of the surface thereof coated with ink to be transferred; a web of sheet material; means for moving said web and causing it to pass closely adjacent said coated surface and with at least a portion of one surface of said web in light contact with a portion of the ink on said coated surface, said contact being insuiiicient to alone effect the desired transfer; a second rotating cylindrical member, this member having conducting means in engagement with the other surface of said sheet, this means comprising a surface layer of conducting readily resilient material; means operative on said web pr'ior to the printing point for increasing the conductivity thereof; and means for passing a current through said sheet and the ink in Contact therewith, this means including both cylindrical members as current carrying elements in the circuit for said current and passing appreciable current across the printing gap between said cylindrical members.

4. The method of printing from a rotating cylindrical member having at least a portion of the surface thereof coated with ink to be transferred to a web of sheet material, comprising moving said web, rendering said web more conductive than normal, causing at least a portion of one surface thereof to come into light contact 85 2,408,144

with at least a portion of the ink on said coated surface, pressing said web lightly against the inked surface with readily resilient conductive means, and simultaneously passing an appreciable current through said web and the ink in contact therewith.

5. The method of printing from a rotating cylindrical member having at least a portion of the surface thereof coated with ink to be transferred to a web of sheet material, comprising moving said web, rendering said web more conductive than normal, causing at least a portion of one surface thereof to come into light contact with at least a portion of the ink on said coated surface, pressing said web lightly against the inked surface with readily resilient conductive means, and simultaneously passing an appreciable current through said web and the ink in contact therewith, the speed of movement of the web being sufficient to prevent scorching of the paper by the current.

WILLIAM J. HOOPER.

REFERENCES CITED- The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name l Date 1,788,600 Smyser Jan. 13, 1931 1,820,194 Huebner Aug. 25, 1931 2,191,827 Benner Feb. 27, 1940 2,224,391 Huebner Dec. 10, 1940 Huebner Sept. 24, 1946 

